Circuit controller



Sept. 29, 1931. c, T EVANS 1,825,312

CIRCUIT CONTROLLER Filed Oct. 17 1925 ILV V EN TOR. (Lia mm :5. 5114411 ATTORNEY Patented Sept. 29, 1931 UNITED STATES PATENT OFFICE CLARENCE T. EVANS, OF \VAUWATOSA, WISCONSIN, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO CUTLER-HAMMER, INC., A CORPORATION OF DELAWARE CIRCUIT CONTROLLER Application filed October 17, 1925.

This invention relates to circuit controllers and more particularly to motor controllers of the type disclosed in the patent to Clarence T. Evans, No. 1,47 9,033, of J anuary 1, 1924.

The controller disclosed in the aforesaid patent employs accelerating switches each having an operating winding and a restraining winding and one or more inductors for supplying transient currents to the restraining windings of said switches to delay-operation thereof. In such a controller response of each accelerating switch may be delayed for an appreciable time which is regulable by adjusting the reluctance of the magnetic circuit of the restraining winding. However, due to the inherent characteristics of the transient currents supplied to the re straining windings relatively slight variations in the reluctance of the magnetic circuits of such windings produce relatively wide variations in the delay effected by such currents. In practice it has been found that where conventional types of accelerating switches are employed it is difficult to obtain the desired accuracy of adjustment of the reluctance of the magnetic circuits of the restraining windings, and it has also been found difiicult to maintain given adjustments due to wear on the pivot parts of the switches.

The present invention has among its objects to provide an improved accelerating switch for systems of the aforesaid character which will overcome the aforementioned difliculties.

Another object is to provide an accelerating switch for systems of the aforesaid character having an adjustment to definitely limit the time interval and an adjustment to afford variation of the time interval with a high degree of accuracy.

Various other objects and advantages of g the invention will hereinafter appear.

The accompanying drawings illustrates an embodiment of the invention which will now be described, it being understood that the embodiment illustrated may be modified in certain respects without departing from the spirit and scope of the appended claims.

Serial No. 62,989.

switches 2, 3 and 4, switch. 1 being employed to control the continuity of the armature circuit of a shunt motor M, and switches 2, 3 and 4 to control starting resistances R R and R connected in series with the motor armature. The aforesaid switches are each provided with a shunt operating winding A, the shunt operating Winding of switch 1 being controlled by a manual switch 9 and the shunt operating windings of switches 2, 3 and 4 being controlled by auxiliary contacts 1, 2 and 3", respectively, in a well known manner to provide for operation of all of said switches sequentially in the order of their reference numerals. Switches 2, 3 and 4 are each provided with a restraining winding B which affords means for delaying closure thereof, but only so long as said windings are supplied with a given current. As illustrated in Fig. 1, the restraining windings B of switches 2, 3 and 4 are respectively supplied with current by inductors 10, 11 and 12, it being understood that other means for supplying transient currents might be substituted for such inductors. Each of the inductors is providedwith a primary winding 18 to be included in I series in the motor armature and a secondary winding 14 to supply current to its respective restraining winding.

The circuit arrangement is such that closure of switch 1 completes circuit from line L by conductor 15 through said switch, by conductors 16 and 17 through the primary winding of inductor 10, by conductor 18 through resistance R by conductor 19 through resistance R by conductor 20 through resistance R, by conductor 21 through armature A of the motor to line L the field of the motor being directly connected between lines L and L Under such conditions, the inductors 11 and 12 are disconnected from circuit, but upon closure of switch 2 the motor circuit extends from switch 1 by conductor 16 through switch 2 by conductor 22 through the primary winding of inductor 11, by conductor 23 to conductor l9, and thence through resistances R and R to the motor armature. This shortcircuits resistance R and the inductor 10, and upon closure of switch 3the motor circuit extends from switch 2 by conductors 22 and 24 through switch 3, by conductor 25 through the primary winding of inductor 12, by conductor 26 to conductor 20 and thence through resistance R to the motor armature. This short-circuits resistance R and the inductor 11, and upon closure of switch 4 the motor circuit extends from switch 3 by conductors 25 and 2'? through switch 4 direct to the motor armature, thus short-circuiting resistance R- and the inductor 12.

From the foregoing it is apparent that upon initial closure of the motor circuit the primary winding of inductor 10 is subjected to the armature current, and the rise in armature current from zero value causes said inductor to supply an induced current in the circuit of the restraining winding B of switch 2. Similarly, upon closure of swtches 2 and 3 the inductors l1 and 12 are successively subjected to currents rising from zero value, whereby they also function to supply induced transient currents to the rest 'aining windings B of their respective switches. The secondary current thus supplied to each restraining winding has a time constant determined by the design of the inductor and its connected circuits, and a rising current in the primary of each inductor tends to prolong the secondary current, while a decrease in primary current has a reverse tendency. Hence, by proper design of the inductors and their connected circuits, response of each accelerating switch may be delayed for an appreciable time augmented by the time element of such switch and regulabie by adjustment of the air gap between the core of the restraining winding and the switch part attracted thereby.

As before stated it has been found that the characteristics of the induced currents supplied to the restraining windings is such that slight variations in the reluctance of the magnetic circuits of the restraining windings produce relatively wide variations in the delay effected by such transient currents. According to the present invention, the reluctance of the magnetic circuit of each of the restraining windings is varied by means of two adjustable air gaps in such circuit, one of such air gaps to be set to limit the tme interval and the other being adjustable to afford variation of the time interval. \Vhile such adjustments may be effected in numerous ways, each of the switches 2, 3 and 4 is preferably constructed as shown in Figs. 2, 3 and 4.

As shown in Fig. 3, each accelerating switch is mounted upon an insulating panel 30 and the shunt operating coil A is provided with a U-shaped frame fixed to said insulating panel, said frame including an L-shaped magnetic part- 31 fixed to base 30 and av magnetic center pole 32. The switch is provided with an operating armature 33 which is pivotally mounted intermediate its ends upon a pin 34 carried by the member 31. The movable contact 35 of the switch is fixed to an arm 36 which is pivotally secured at 37 to the upper end of armature member 33 and said contact is yieldingly held in the position shown by a spring 38. The stationary contact- 39 of the switch is carried by a bracket 40 fixed to panel 30, and, if desired, a blowout device may be arranged as shown, said device including a coil 41 connected between a binding post 42 and the bracket 40. The binding post 42 forms one terminal of the switch and the opposite terminal comprises a binding post 43 which is connected to contact 35 by a flexible connection 44.

The restraining winding B is arranged adjacent the lower end of the armature member 33 and as best shown in Fig. 4 the same is provided with a central magnetic sleeve 45 having insulating washers 46 and 47 arranged adjacent opposite ends thereof. lVasher 46 is held in place by a magnetic plate 48 which is secured to sleeve 45 by riveting the end of said sleeve over said plate as shown at 49. Washer 47 is held in place by a magnetic washer 50 which is fixed to the sleeve 45 by riveting the latter over said washer as shown at 51. The coil B is provided with a magnet frame 52 which is fixed to insulating panel 30 and said coil is slidably mounted upon a magnetic post 53 fixed to the panel 30 and provided with a non-magnetic cap 54 on its outer end. The position of winding B with respect to the face of cap 54 is determined by shims which are arranged between plate 48 and the magnetic frame 52. As best shown in Fig. 2 each of the shims 55 is provided with a slotted opening intermediate the ends thereof and each is also provided adjacent opposite ends with openings for receiving screws 56 which are threaded into the bracket 52 and are provided with heads for engaging the outer face of plate 48.

In connection with the foregoing it should be noted that the non-magnetic cap 54 forms a stop for the armature 33 and by loosening screws 56 the number of shims 55 may be varied as desired for variation of the air gap between washer 50 and the lower end of armature 33. In practice such air gap is adjusted to insure response of the switch after a given maximum interval, and it should be noted that such air gap will be uneffected by Wear on the pivot parts of the switch.

With winding B set in a given position variation of the time interval of the switch is effected by means of a magnetic adjusting screw 58 which is threaded into an opening in a projection 59 on magnet frame 52. Projection 59 is split at one side thereof as shown in Fig. 2, and is provided with a bolt 60 for clamping the adjusting screw 58 when the latter is set in a given position. Thus the air gap between the end of said screw and armature 33 may be varied as desired, to effect variation of the time interval of the switch after limiting of such interval by the shim adjustment of winding B.

In connection with the foregoing, it should be noted that the aforesaid switch is particularly adapted for use in connection with controllers of the character disclosed in Fig. 1, since the shim adjustment provides for wide variations in the reluctance of the magnetic circuit of the restraining winding to adapt the switch for use in connection with controllers having varying numbers of resistance steps, while the adjusting screw 58 serves to effect relatively fine variations in the reluctance of the magnetic circuit of the restraining winding to provide for proper timing of the switches.

As before stated, certain of the accelerating switches are provided with auxiliary contacts for controlling the operation of the next switch of the sequence, and, as shown in Figs. 2 and 3 such auxiliary contacts may comprise contact fingers 62 and 63 which are secured to panel 30 and a cooperating insulated bridging contact 64 which is secured to the armature member 33 adjacent the lower end thereof.

What I claim as new and desire to secure by Letters Patent is:

1. An electromagnetic switch having a pivoted operating armature, electromagnetic means associated with said armature for restraining the same against movement from a given position, said means including a fixed magnet frame having a projection thereon, a winding mounted on said projection and having a core member fixed therein, a non-magnetic stop mounted on the end of said projection to limit movement of said armature and means for adjusting said winding axially on said projection to provide a variable air gap between said core member 65 and said armature while maintaining the reluctance of the iron circuit for said winding substantially constant.

2. An electromagnetic switch having a pivoted operating armature, electromagnetic means associated with said armature for restraining the same against movement from a given position, said means including a fixed magnet frame having a projection thereon, a winding mounted on said projection and having a core member fixed therein, a non-magnetic stop mounted on the end of said projection to engage said armature, and means for adjusting said winding and the core member therein with respect to said armature, said means including a plurality of removable magnetic shims between said frame and the core member of said winding.

3. An electromagnetic switch having a.

pivoted operating armature, electromagnetic means associated with said armature for restraining the same against movement from a given position, said means including a frame having pole extensions thereon, one of said extensions having a non-magnetic stop on the extremity thereof for engaging said armature and the other being adjustably mounted on said frame for variation of the air gap between the same and said armature and a winding mounted on said former pole extension, said winding having a magnetic core member therein and being adjustable axially on said former pole projection and means including a plurality of removable magnetic shims between said frame and said'core for maintaining said winding and the core therein in their adjusted positions on said former pole extension.

In witness whereof, I have hereunto subscribed my name.

CLARENCE T. EVANS. 

